SB-021 Service notes on TS-520 10-21-77 TRANSMITTER 1. No switching of final relay: Bad Q8 on X54-0001-00 2SA562Y. 2. No drive: C3 100pf in final box is cold soldered. 3. Low output: Check the plate load cap for touching plates. 4. 3.5 MHz low output: Replace burned 47pf 3KV at load wafer. 5. No TX: Final choke burned out in final VOX L8. 6. No RX or TX: Bad common amp. Q1 3SK35GR in IF unit X48-1060-00. 7. No ACC: No plate current Q2 3SK41 If unit X48-1060-00. 8. No TX relay: Q8 2SA562Y on VOX unit. Also R18 1K resistor relay control. 9. No TX or RX: Check 9 volt terminal on FIX AVR (X43-1100-00) is loose. 10. No CW TX: Bad 9 volt regulator. Check D3 WZ061 on X43-1100-00. 11. No TX: Solder touch between TIF and key terminal on X44-1080-00. 12. No drive to TX: Check RL1 on GEN unit, small reed relay (X52-0010- 01). 13. No ALC meter action on 10 meters: This is normal for TS-520. 14. CW chirp: Q4 2SA606L on Fix channel AVR X43-1100-00. 15. ALC meter to maximum when TX: RFI terminal at X44-1080-00 is not soldered. 16. No TX output: 82pf 3KV in final is burned. 17. No TX output: Q3 on RF unit 3SK41 X44-1080-00. 18. No bias: 10 ohm cathode resistors burned in final VOX. 19. No drive or TX output: R70-71 RF unit, R5 Rectifier unit. 20. No VOX: Q8 in VOX unit X54-0001-00. 21. No TX: 12BY7 is bad. Shorts and burns out. R71 and 70. 22. No carrier output: Q1 on Carrier X50-0009-01. 23. No drive - no screen voltage: R5 470 ohm open on rectifier X43-1090- 00. 24. No drive - no ALC: Q2 3SK35Y IF unit. Q3 3SK41L RF unit. 25. No RF output: C13 0.04uf at pin 1 of S2001A is bad. 26. Low mic gain: Q1 2SC1000 on Gen unit. 27. No TX: Misconnection of brown wire after installation of CW filter. RECEIVER 1. Low Sensitivity: Touching RLT and 9V at function switch. 2. Receiver sensitivity: No -6v at AVR: Q8 2SC735 on X43-1100-00 is bad. 3. Frequency Shift: Bad carreir Xtal 3395 on carrier unit. 4. VFO drift: C6 22pf, VFO unit. 5. No receive: Bad Q4, 3rd IF amp 3SK35GR on X48-1060-00. 6. Receiver sensitivity and bias current jump, -6v unstable: T1 oscillator transformer for -6v is bad on X43-1100-00. 7. Erratic AGC action: C11 100uf 16Von X431100-00. Fix channel AVR is bad. 8. Frequency shift when warmed up: Q1 in VFO 3SK22GR. 9. No RX or TX: If unit C59 touch to T12 IF transformer. 10. Receiver noise: Q5 3SK35Y X44-1080-00. 11. Receiver sensitivity down: NBI terminal is pulled loose. Receiver at IF board. 12. No S meter reading and RF gain CCW. No meter deflection: Q3 on IF unit. Q5 on RF unit. 13. VFO frequency jumped: There is loose tension inside VFO. 14. VFO frequency shift: Cold solder of VFO output lead to VFO output socket. 15. Blows fuse when first on: Check Q1 and Q2 DC-DC converter transistor. One is possibly shorted. 16. Noise blanker inoperative: R6 4.7K resistor is broken at Q2 on X54- 1080-10. 17. Loud audio squeal: Q4 3SB473 on X49-0008-01 shorted. 18. Low receiver sensitivity: Diode D4 1S1587 on RF unit. 19. VFO intermittant: Wire to L1 in VFO is not soldered. 20. No receive: Q4 3SK35Y, Q5 3SK35GR on RF unit. 21. No receive: Q9 3SK35GR on IF unit. 22. Hash noise in receiver: Q3 on RF unit 3SK41. 23. Blows fuse: C31 power supply is shorted, 100uf 500v. Also check associated diode D3, D4. 24. No RX on all bands: WWV switch is broken or a wire is loose or not soldered. 25. Receiver sensitivity: Q5 on RF amp 3SK35Y. 26. Receiver sensitivity: NBO terminal on X48-1060-00 is loose. 27. Low audio: Check for purple wire touch to ground at 12 pin connector in rear panel. (c) 102177TKC